Rotary impulse sprinklers include a main body which can rotate about a vertical axis. This body pivotally carries an impulse arm which can independently rotate about the vertical axis. Water dispensed by a nozzle held on the main body causes deflection of the arm. A reversing mechanism held by the main body limits the extent of deflection of the arm so that the main body rotates about the vertical axis in a fast step-by-step fashion, for example, through an angle of about 2 degrees as a result of each deflection. The arm is biased into position for deflection by a helical tension spring acting upon both the main body and the impulse arm. Upon the main body reaching a predetermined angular position, a reversing mechanism is actuated which permits the impulse arm to swing through a much greater angular distance with each oscillation resulting in the main body returning toward its predetermined starting position where the reversing mechanism is again switched. This return movement is in a slow step-by-step fashion with the arm returning through an angle of about 5 degrees per deflection. Of course, the reversing mechanism can be disabled resulting in full circle operation in either the fast step mode or the slow step mode, depending on the position of the reversing mechanism.
Such impulse sprinklers commonly are equipped with deflectors carried by the main body overlying the nozzle for limiting the radial excursion of the dispensed water. These deflectors are formed by several separate components and require the use of a tool or both hands of the operator for adjustment. Furthermore, the use of such a deflector results in the diffusion of the water so that the water cannot be accurately limited to the ground area desired to be covered, resulting in overspray.
For example, one such sprinkler includes a deflector block pivotally mounted by pins on the sprinkler main body. The inclination of the block is controlled by a cam surface on a knob acting against one end of the pivotable block. A spring is required to maintain the block end in engagement with the cam surface. For further information concerning the structure and operation of such prior art impulse sprinklers, reference may be made to U.S. Pat. Nos. 4,497,441 and 3,070,314.